24 BULLETIN 741,. U. S. DEPARTMENT OF AGRICULTTJRE. 
under its own shade Light thinnings are of some value, but a very 
large percentage of the sprouts soon succumb because of insufficient 
sunjight. The surviving sprouts are forced into intensive competi- 
tion with various shade-enduring, aggressive, shrubby, and herba- 
ceous species. This, coupled with inadequate light, renders the 
sprouts weak and not uncommonly diseased. If the slender speci- 
mens are not killed outright by fungous attacks, sooner or later 
they fall easy victims to the wind. 
The average stand of prop timber, the diameter breast-high of which 
does not exceed 10 inches, consists of about 480 trees per acre. To 
insure a stand of this number of trees at the average rate of mortality 
of the sprouts, a stand of 2,500 specimens per acre the third year 
after cutting is sufficient, even though the lands are moderately 
grazed by cattle or sheep after the terminal shoots are no longer 
subject to browsing. In practically any type of aspen properly 
protected from stock, the stand following clear-cutting will generally 
be 2,500 specimens per acre. Thus in the case of the plot pictured 
in figure 2 of Plate V, representing the sprouting capacity following 
the clear-cutting of an 80-year old stand, there are more than 30,000 
specimens at the end of the third year. The sprouting appears to 
be quite as vigorous when younger stands are clear-cut. 
METHODS OF BRUSH DISPOSAL. 
Various methods of disposing of the brush are in practice, some 
of which tend to expose the sprouts unduly and others to protect 
them. Piling and burning the brush is the most popular; but this 
method, owing to the complete opening up of the lands, is responsible 
for highly destructive browsing, especially by sheep, the result being 
that the stand is materially thinned and correspondingly mutilated. 
The method appears to endanger the establishment of the stand 
approximately in proportion to the number of spaces burned. 
Experiments have been made in scattering the brush over the cut- 
ting without lopping the nonmerchantable parts. The method which 
has given the best results, and which at the same time lends itself to 
general field practice, is that of scattering the unlopped ones about 
the stumps, the butts of the discarded portions being placed next 
to the stumps in such a manner as to have the branches extend out 
in all directions from the stump. Since the major portion of the 
reproduction originates from superficial roots near the parent plant, 
the tops are located where they will afford the greatest possible 
protection to the new sprouts. 
This light screen of unlopped branches, arranged as described., is 
surprisingly effective against repeated visitations by sheep during 
the first three seasons after the cutting, which is the most critic a] 
period. While, to be sure, there is usually not a sufficient supply of 
